What’s next for ESA’s ExoMars mission?
ExoMars. The word elicits images of a mission fraught with change, turmoil, and misfortune. ExoMars is a mission that has persistently pushed past hurdle after hurdle to make its way to the Red Planet. With the recent loss of the Schiaparelli lander, that trend does not appear to be changing.
The Exobiology on Mars (ExoMars) mission is designed to study the possibility Mars had the ability to support life. It is also hoped that ExoMars will serve as a test bed for new technologies that could be used to explore the planet on future flights. The end goal of this latter initiative would be a sample return mission that would be conducted sometime in the 2020s.
Recent events have provided another troubling chapter in the mission’s history.
The two elements of the mission that have completed the 33-million mile (54 million km) journey to Mars were the Trace Gas Orbiter (TGO) and the Entry, Descent and Landing Demonstrator Module (EDM) called “Schiaparelli“.
After passing a number of obstacles, the first part of the mission got underway on March 14, 2016, launching atop a Proton-M rocket from Baikonur Cosmodrome in Kazakhstan.
On Oct. 16, Schiaparelli departed from the TGO (which arrived in orbit above the Red Planet on Oct. 19, 2016). It quickly became apparent the test lander, Schiaparelli, had encountered something “off nominal”. In short, the lander was lost on entering Mars’ thin atmosphere (about one percent of Earth’s and comprised primarily of carbon dioxide).
Five days after it had parted ways with the TGO, NASA’s Mars Reconnaissance Orbiter sent back images showing the lander’s crash site as well as the parachute it employed during its landing attempt.
“Schiaparelli’s primary role was to test European landing technologies,” said Jan Worner, ESA’s Director General. “Recording the data during the descent was part of that, and it is important we can learn what happened, in order to prepare for the future.”
About a month later, on Nov. 23, ESA announced it had been making progress on the Schiaparelli anomaly investigation. Data indicated that the parachute deployed normally at 7.5 miles (12 kilometers) while traveling 1,075 mph (1,730 km/h). The heat shield was released as planned at 4.8 miles (7.8 kilometers).
“As Schiaparelli descended under its parachute, its radar Doppler altimeter functioned correctly and the measurements were included in the guidance, navigation and control system,” an ESA press release stated. “However, saturation – maximum measurement – of the Inertial Measurement Unit (IMU) had occurred shortly after parachute deployment.”
According to ESA, the IMU measures the rotation rates of the vehicle and its data was generally predicted – except for this particular event. The saturation lasted for about one second. As such, when the data was compiled into the navigation system, the information generated estimated an altitude that was negative – below ground level.
“This in turn successively triggered a premature release of the parachute and the backshell, a brief firing of the braking thrusters and finally activation of the on-ground systems as if Schiaparelli had already landed,” the release stated. “In reality, the vehicle was still at an altitude of around 3.7 kilometers.”
All of this data has been reproduced in computer simulations on Earth. However, ESA’s David Parker, director of Human Spaceflight and Robotic Exploration, said this is still a very preliminary conclusion.
“The full picture will be provided in early 2017 by the future report of an external independent inquiry board, which is now being set up, as requested by ESA’s Director General, under the chairmanship of ESA’s Inspector General,” Parker said.
The ExoMars program has a long history of misfortune, and the loss of Schiaparelli was just the latest disappointment for a mission that got its start almost 11 years ago.
ExoMars got its start in December of 2005 as a part of the European Space Agency’s Aurora Programme when ESA’s ministers gave it the green light. The mission was originally conceived as consisting of a rover and a ground station which was supposed to have launched in 2011 atop a Russian Soyuz Fregat rocket.
In 2007, MacDonald Dettwiler and Associates Ltd. (MDA), a Canadian tech firm, was tapped to design and build a prototype Mars rover chassis for ESA under a one-million-euro contract with British-based EADS Astrium.
Fast forward about two years and what would eventually become the ExoMars mission was known as the Mars Exploration Joint Initiative (MEJI) with NASA. The U.S. space agency would contribute a United Launch Alliance (ULA) Atlas V rocket under this agreement.
By switching from a Soyuz rocket to ULA’s Atlas V, the specifics of the spacecraft altered dramatically. As if the mission had not changed enough, it would continue to be modified to include two Atlas flights, and a second rover, MAX-C, was also considered.
An array of other proposals came and went before an all too familiar issue raised its head – that of limited funding.
NASA backed out of the agreement on Feb. 13, 2012, due to the U.S. space agency having its funding for the project canceled under President Barack Obama’s FY2013 Budget. This set the stage for a renewed agreement between ESA and the Russian Federal Space Agency.
With renewed Russian support and the planning and development decided, ExoMars finally left the drawing board and, in 2016, the launch pad. However, a number of spacecraft comprise ExoMars; as noted, two of them have already completed their journey to the Red Planet via a Proton-M rocket.
This past May, it was announced that the mission’s second component would be delayed from 2018 until no-earlier-than 2020 when Mars will again be in the optimal gravitational alignment. The components for this part of the mission include a Russian landing system, a surface platform, and the ExoMars rover itself.
“The Tiger Team has presented their final report on the work that was done at the meeting,” Roscosmos said via a release. “Having assessed the conditions needed for the successful implementation of the project, JESB concluded that, taking into account delays caused by European and Russian contractors’ performance and bilateral deliveries of scientific equipment, it will be best to conduct the launch in 2020.”
The multiple causes of this delay came from both Russian and European contractors. According to ESA, every effort was made to stick to the 2018 launch date. However, in the end, it simply was not to be.
“What we have been doing lately is seeing if we could shorten the assembly, integration and testing phase to something that would be acceptable from a risk point of view, but still make the 2018 launch,” Rolf de Groot, Head of ESA’s Robotic Exploration Coordination Office, told BBC. “Very recently, we have concluded that this is not possible without adding a large amount of additional risk to an already risky mission. So, we decided the only responsible thing to do was move to the 2020 launch date.”
ESA and Roscosmos are not alone in having a high-profile mission to the Red Planet be pushed back. NASA, the U.S. space agency, announced earlier this year (2016) that the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission would not launch this year but would be pushed back to no-earlier-than May of 2018.
The cause of this launch date slip was identified as a vacuum leak in the spacecraft’s primary scientific instrument – the Seismic Experiment for Interior Structure (SEIS) that the InSight lander would bring with it to the surface of Mars.
However, not all of the news about automated missions to Mars has been bad.
The Trace Gas Orbiter component of ExoMars, while it was en route to the Red Planet, snapped its first images of its target this past June.
“The images have confirmed the sensitivity of the instrument and are sharp. It seems to be well-focused and the signal level seems to be close to prediction,” said Antoine Pommerol, co-investigator of the Colour and Stereo Surface Imaging System (CaSSIS), shortly after the images were released.
This was not the first time that CaSSIS was activated. The instrument was first activated back on April 7, 2016. Rather than capturing an image of the Red Planet, the device was used to take a picture of a randomly selected area of space. While this might not seem all that useful, the pictured allowed mission planners to identify a group of stars.
“The initial switch-on went quite smoothly and so far things look good,” said Nicolas Thomas, the camera principal investigator at the University of Bern. “If the instrument continues to perform well, indications are that we should begin to exceed what is achievable from Earth in the second week of October, and then further improvements in resolution will happen rapidly.”
With the loss of Schiaparelli, ESA is reviewing what went right and what went wrong with its descent. Given that ExoMars’ rover has been rescheduled to launch sometime in 2020, the lessons that can be gleaned from what had occurred should serve to improve future descent vehicles. Europe’s space agency hopes that this pragmatic approach will lessen the likelihood that future robotic pathfinders will meet the same fate as Schiaparelli.
“In terms of the Schiaparelli test module, we have data coming back that allow us to fully understand the steps that did occur, and why the soft landing did not occur,” Parker said.
— UPDATE added at 2:01 p.m. EDT on Monday, Nov. 28:
A report appearing on Mars Daily, noted that the mission’s woes appear to be ongoing, as the European Space Agency asked member nations on Friday Nov. 25 for an additional an extra 400 million euros ($425 million) to complete the mission.
Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.